April Fools Day Contest 2021

Solutions for April Fools Day Contest 2021 (contest 1505). 6/9 problems verified against sample I/O. Difficulty range: 900-2600.

9 items

April Fools Day Contest 2021

Type: April Fools | Problems: 9 | Verified: 6/9 | Rating range: 900-2600 | Time: 32m 41s

Problem	Name	Rating	Tags	Solve Time	Verified
A	Is it rated - 2	900	*special, implementation, interactive	7m 52s	✓
B	DMCA	1600	*special, implementation, number-theory	5m 40s	✗
C	Fibonacci Words	1400	*special, implementation	3m 11s	✓
D	Xenolith? Hippodrome?	1800	*special, number-theory	2m 17s	✓
E	Cakewalk	1800	*special, greedy, implementation	2m 3s	✓
F	Math	2200	*special, math	5m 35s	✗
G	Encoded message	2600	*special, implementation	3m 14s	✗
H	L BREAK into program	2500	*special	1m 20s	✓
I	Mysterious language again, seriously?	2200	*special	1m 29s	✓

Practice › Codeforces Solutions › April Fools Day Contest 2021 ›

CF 1505F - Math

The statement is given as a picture, but the task itself is extremely small. We receive a single integer a, whose value lies between -100 and 100.

Practice › Codeforces Solutions › April Fools Day Contest 2021 ›

CF 1505G - Encoded message

We are given up to 24 small “blocks”. Each block contains five integers. The first three numbers are in the range 0 to 2, and the last two are in the range 0 to 3.

Practice › Codeforces Solutions › April Fools Day Contest 2021 ›

CF 1505I - Mysterious language again, seriously?

This is one of Codeforces's special problems. There is no conventional algorithmic input. Instead, contestants were given access to a language hidden behind the codename "Secret 2021" in the Custom Test environment and had to determine what real programming language it…

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CF 1505H - L BREAK into program

The challenge of Codeforces 1505H is less about parsing standard input or performing calculations, and more about understanding the hidden logic embedded in a binary program. The “input” is effectively empty because the program does not provide us with data.

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CF 1505A - Is it rated - 2

The runtime error here is a simple input parsing mistake. The input has a test case format where each test case consists of a number n followed by a string of length n. The previous code assumes that the first line of each test case contains two integers (n k), which is wrong.

Practice › Codeforces Solutions › April Fools Day Contest 2021 ›

CF 1505E - Cakewalk

We are given a small rectangular cake divided into a grid of squares. Each square either has a berry or is empty. The mouse starts at the top-left corner of the cake and can only move right or down until it reaches the bottom-right corner.

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CF 1505B - DMCA

The task hides the familiar notion of a digital root behind unusual terminology. We are given a positive integer and need to repeatedly replace it by the sum of its decimal digits until only a single digit remains. That final digit is the answer.

Practice › Codeforces Solutions › April Fools Day Contest 2021 ›

CF 1505D - Xenolith? Hippodrome?

We are asked to determine whether a certain number $N$ can be expressed as a sum of powers of an integer $M$, with each power used at most once. Equivalently, we want to know if $N$ has a representation in base $M$ using only digits 0 or 1.

Practice › Codeforces Solutions › April Fools Day Contest 2021 ›

CF 1505C - Fibonacci Words

We are given a string of uppercase letters between length 1 and 10. Our task is to determine whether it is possible to arrange the letters consecutively so that each letter (except possibly the first and last) has neighbors in the string corresponding to letters that differ by…